Toplink btach update without select ?

Question

My customer must update a table of 50 millions records with new value of column from a flat file.
We decided to use the TopLink BatchUpdate functionality but we noted that it was necessary to read the objects before updating them !
The scenario is following :
1- Read lines of flat file : id + new value of column(s)
2- Construct object and Appply functionnal rules
3- Use TopLink BatchUpdate to update database table
In Toplink we are obliged to add an additional stage:
<<reading of all the objects from the database (50 million) before updating them ! >>
We seriously thinks of rewriting in jdbc with statement.addBatch() and without 50 millions select on database.
I know that CoCoBase also update objects without read them.
you have other solutions ?
Thank you

Answer 1

You can use a DatabaseSession and updateObject to update objects without reading them.
i.e.
// Map the fields being updated in your project, configure login to use parameter batch writing, (ideally configure cache to NoIdentityMap if the objects are simple as well).
DatabaseSession session = MyProject.createDatabaseSession();
while (! fileStream.atEnd()) {
List nextBatchOfObjects = readNext100ObjectsFromFile(fileStream);
session.beginTransaction();
for (Iterator iterator = nextBatchOfObjects.iterator(); iterator.hasNext(); ) {
MyObject object = (MyObject) iterator.next();
session.updateObject(object);
session.commitTransaction();
session.initializeIdentityMap(); // (if not using NoIdentityMap).
You could also use writeObject or even unit of work if you use a does exist policy with something other than checkCache (i.e. assumeExistence()). You could even use registerExistingObject on unit of work, however you must make sure you change the objects from the file data after registration.